docs: def _load(self, filename=None):
          """Read the AATSR rsr data"""
          if not filename:
              filename = self.aatsr_path
  
          wb_ = open_workbook(filename)
  
          for sheet in wb_.sheets():
              ch_name = sheet.name.strip()
              if ch_name == 'aatsr_' + self.bandname:
  
                  data = np.array([s.split() for s in
                                   sheet.col_values(0,
                                                    start_rowx=3, end_rowx=258)])
                  data = data.astype('f')
                  wvl = data[:, 0]
                  resp = data[:, 1]
  
                  self.rsr = {'wavelength': wvl, 'response': resp}